Siloxane−TiO 2 Hybrid Nanocomposites. The Structure of the Hydrophobic Layer

Anatase−brookite titanium dioxide nanoparticles are derivatized with two commercial trifunctional siloxanes by a mild impregnation method. The filmed titania nanoparticles are characterized by X-ray diffraction, N 2 adsorption at subcritical temperatures (BET and BJH methods), and contact angle determinations. Starting from siloxane contents of 9%, the particles show highly hydrophobic properties (contact angle around 140−150°), complete buoyancy over water, and excellent self-cleaning properties. Solid-state 29 Si cross-polarization magic angle spinning nuclear magnetic resonance ( 29 Si CP/MAS NMR) is used to investigate the mode of attachment of the siloxane molecules to the TiO 2 surface. The combination of these results with X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy provides unique information on the structure of the chemisorbed siloxane layer. The siloxane groups covalently attached to the TiO 2 surface may serve as powerful linkers for different functionalities.